Well I was going to wait till winter for the next one but have started fiddling with the left over bits from the plunger.
There is pretty much a complete longstroke engine in boxes, including rebored barrels, reground crank new hepolite pistons.
Only problem is this was done in 1971 & with the exception of the pistons is all rather rusty!
Anyway, the timing side crankpin has only one oil hole drilled.
Have removed sludge trap plugs & there is no evidence that ever was a hole in one half of the crankpin.
My original thought was a shell must have seized into it but looking from inside of sludgetrap it is completely undrilled!
Have spoken to SRM, the guy I spoke to has seen some early cranks like this, he recommends drilling it out.
So that's the engineering perspective.
My lazy perspective: I'm thinking well it's been like this since nineteen fourty something & is only on second regrind both crankpins same size so maybe one hole is enough.
Theory 1: BSA special experiment, one hole supplies enough oil to crankpin/shells while increasing residual oil pressure to troublesome T/S bush which needs it more.
Theory 2: This is a "Friday afternoon" crank.
Anyone had similar experience, run a crank like this, have any other theories, want to shoot my brilliant theories down in flames?
Cheers,
Rusty
